body,h1,table{
    /*margin:0;*/
    /*padding: 0;*/
}
.dv{
    width: 400px;
    height: 350px;
    margin: 0px auto;
    border:8px solid royalblue;
}

.dv table{
    width:300px;
    margin-left: 50px;
    /*表格的实线*/
    border-collapse: collapse;
}

tr,th,td{
    width: 60px;
    line-height: 30px;
    text-align: center;
}

